/Engine/Source/Runtime/ApplicationCore/Public/GenericPlatform/ITextInputMethodSystem.h
Sets the range of code point indices that are selected and which end of the selection the caret is at.
void SetSelectionRange ( const uint32 InBeginIndex, const uint32 InLength, const [ECaretPosition](API\Runtime\ApplicationCore\GenericPlatform\ITextInputMethodContext\ECaretPosition) InCaretPosition )